We present a novel way of wavefront sensing using a commercially available, continuous-wave time-of-flight camera with quarter video graphics array resolution. This CMOS phase camera is capable of sensing externally modulated light sources with frequencies up to 100 MHz. The high-spatial-resolution of the sensor, combined with our integrated control electronics, allows the camera to image power modulation index as low as $-62\mathrm{dBc}/\sec /\mathrm{pixel}$. The phase camera is applicable to problems where alignment and mode-mismatch sensing is needed and suited for diagnostic and control applications in gravitational-wave detectors. Specifically, we explore the use of the phase camera in sensing the beat signals due to thermal distortions from pointlike heat absorbers on the test masses in the Advanced LIGO detectors. The camera is capable of sensing optical path distortions greater than about 2 nm in the Advanced LIGO input mirrors, limited by the phase resolution. In homodyne readout, the performance can reach up to 0.1 nm, limited by the modulation amplitude sensitivity.

• Received 13 May 2021
• Accepted 29 June 2021

DOI:https://doi.org/10.1103/PhysRevD.104.042002